Although the following description of the present invention relates to a thru-axle system for securing a wheel to a bicycle, it is understood that the invention is not restricted thereto, but that as readily appreciated by the person skilled in the art it can apply just as well to motorcycles or any other subject matter where wheels are secured to a moveable devise.
Thru-axle systems for securing wheels are known from prior art examples which are usually engineered for securing wheels to the fork or frame dropouts of a bicycle. These prior art systems mostly comprise circular lead-throughs. The hub of a wheel is located between the lead-throughs. The axle is inserted through the hub and the lead-throughs and the wheel is locked in place by means of a bolt fastener and/or quick-release mechanism at the dropouts. To facilitate inserting the thru-axle the lead-throughs at the dropouts as well as the axle mount of the hub, the lead-throughs often have an inner diameter which is roughly 0.5 mm to 2 mm larger in diameter than the outer diameter of the thru-axle.
Experience with such prior art thru-axle system has shown that this difference in diameter between the axle in the dropouts can become unstable. The instability occurs when the wheel moves relative to the fork or frame. This may be caused, for example, by stress due to normal use of the bicycle, but is often caused by the user who either tightens the thru-axle too much or too little.
To avoid these drawbacks WO 2005/051753 discloses a thru-axle system in which the thru-axle with a threaded end that is inserted through a circular lead-through in a first dropout of a bicycle fork and screwed into a threaded receiver cap disposed at the opposite end. The tubular thru-axle is longitudinally slotted at both ends so that both ends are splayed by actuating the clamping mechanism that has conical portions on both ends. This reduces the play of the axle relative to the dropouts, producing a relatively secure non-positive connection between the thru-axle and the fork or frame of the bicycle.
Experience has shown, however, that this system carries a high risk of improper installation. For example, it may be screwed in with inadequate torque applied to the threaded cap or the axle may be clamped too weakly by the clamping mechanism. In addition, professional and semi-professional bicyclists require more precisely mounted wheels and more stable connections between the forks and the wheel for their cycling needs.